Impingement cooling has been used in gas turbine engines for some time. Relatively cooler air is taken from the compressor of the engine and passed through a series of holes in an impingement sheet to direct jets of cool air directly onto a surface in need of cooling. For instance in the area downstream from the combustor section of turbine engines impingement cooling has been used to cool the liner to protect parts that may be damaged by high heat from the core gas flow passes over the surface of the liner. The liner has a series of larger holes that are offset from the first series of holes to create a pressure drop that facilitates the airflow across the hot surfaces of the liner. See for instance U.S. Pat. No. 5,782,294.
Certain areas of these liners cannot be adequately cool by impingement air flow because the air supply plenum is blocked by other equipment or structures located in proximity to the impingement sheet. In the past, there have been various structures proposed to indirectly cool the blocked areas. One such structure includes a series of apertures in the sidewall of a cast heat shield that in turn has a second series of apertures in the surface that is co-linear with the liner.